Fans and Air Pollution Control for CFBC Boilers

The process

A circulating fluidised bed boiler recirculates solids through a hot cyclone and loop seal. The primary air fan runs at high pressure to fluidise the bed, the secondary air fan stages combustion, and the ID fan handles the flue gas after the cyclone and ESP. Loop seal and fluidising blowers add high pressure duties around the furnace.

The gas

Circulating fluidised bed boilers return most solids through the cyclone, so the flue gas reaching the fan carries fine ash at moderate loading. Erosion is slower than on an AFBC unit but still sets the wheel design.

Fans in this process

Duty	What it does here	Type usually selected
ID Fan	Sits at the outlet of a boiler, kiln or furnace and draws the flue gas through the plant to the stack.	Backward curved, backward inclined and radial tipped
FD Fan	Supplies combustion air to a boiler or furnace, pushing ambient air through the air heater and into the windbox against the furnace draft.	Backward curved and backward inclined
SA Fan	Supplies the secondary combustion air that completes burning above the grate or around the burner.	Backward curved and backward inclined
PA Fan	Supplies the air that dries the pulverised fuel in the mill and carries it to the burners.	Backward curved and radial tipped
Combustion Air Blower	Feeds a burner with air at the pressure the burner register needs.	Backward curved and radial tipped
Seal Air Blower	Supplies clean air at a pressure above the mill or fan casing pressure to the shaft seals and bearing housings, so pulverised coal cannot enter..	Backward curved and radial
Dust Collector Fan	The fan behind a bag filter, cyclone or multiclone on a dust extraction system.	Backward inclined and radial tipped
Bag Filter Fan	Pulls the process gas through the filter bags and discharges the cleaned gas to the stack.	Backward curved and radial tipped
Fan Silencer	An absorptive silencer at the fan inlet, outlet or in the duct, cutting fan noise with minimum pressure loss..	Silencer
Vent Silencer	Cuts the noise from steam or gas expanding from high pressure to atmosphere at safety valve outlets, start-up vents and blow-down lines..	Silencer
Ventilation Fan	Moves air through a plant or building for fresh air supply, heat removal and fume dilution where the system is ducted.	Backward inclined and forward curved
High Pressure Blower	Delivers combustion, aeration and conveying air where the system resistance runs to several thousand millimetres of water column in a single stage..	Backward curved and radial tipped

Industries

Related processes